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May 23, 2013
 |  BC Innovations  |  Tools & Techniques

Finding a home for nuclear transfer

Oregon Health & Science University researchers have for the first time generated stable lines of human embryonic stem cells via somatic cell nuclear transfer.1 Whether the platform can carve a niche among existing stem cell-based techniques will hinge on how the cells compare with those generated through other approaches.

Generating embryonic stem cells (ESCs) via somatic cell nuclear transfer (SCNT) involves taking an unfertilized oocyte, removing its nucleus and then transplanting the nucleus of a somatic cell into the enucleated oocyte. The resulting cell is then activated and allowed to divide until a blastocyst is formed. ESCs are collected from this blastocyst and used to establish cell lines.

Researchers in the stem cell space have previously reported on the use of SCNT to generate ESC lines from a range of lab animals,2 including nonhuman primates in a study led by Shoukhrat Mitalipov and published in Nature in 2007.3

Mitalipov is an associate scientist in the Division of Reproductive and Developmental Sciences in the Oregon National Primate Research Center at OHSU.

The next hurdle was to use SCNT to generate ESC lines from human cells. However, early attempts to do so were not successful because human cells generated through SCNT typically stopped dividing after only a few rounds-a phenomenon called early embryonic arrest.4,5

SCNT had been further sidelined owing to the limited supply of donor oocytes and the advent of induced pluripotent stem (iPS) cell technologies.6 The latter are easier to use, more scalable and subject to fewer funding restrictions and ethical considerations than SCNT.

Now, Mitalipov's group at OHSU has reported a protocol that enables the generation of stable human ESC (hESC) lines from cells obtained via SCNT. The researchers used SCNT to fuse fibroblasts from a human cell line with enucleated donor oocytes and then activated the resulting cells.

In culture medium containing caffeine, a subset of the activated cells continued to divide past the early embryonic stage and formed blastocysts. The researchers were able to derive stable ESC lines from these blastocysts. The OHSU group reported in 2007 that adding caffeine to culture medium improved the development of SCNT-generated nonhuman primate cells into blastocysts.7

In the current study, the resulting ESCs expressed known pluripotency markers, formed teratomas when injected into mice and inherited the genome of the donor fibroblast.

Importantly, and contrary to earlier assumptions that deriving an hESC line by SCNT would require unfeasible quantities of donor oocytes,8 the researchers were able...

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